Decorative foil

ABSTRACT

A decorative foil is in the form of a layer composite structure ( 1 ) and comprises at least a transparent base foil ( 2 ), a transparent cover layer ( 4 ) and a transparent dielectric layer ( 3 ) arranged between the base foil ( 2 ) and the cover layer ( 4 ). When the decorative foil serves as a lamination foil for a substrate ( 5 ) the material of the cover layer ( 4 ) is an adhesive. A reflective metallic layer ( 6 ) is arranged at least in surface portions between the dielectric layer ( 3 ) and the cover layer ( 4 ) and optionally a metal film ( 11 ) is also arranged on the side of the dielectric layer ( 3 ) facing the base foil ( 2 ). General items of information shown by the decorative foil are produced by means of modulation of the thickness (s) of the dielectric layer ( 3 ). Transparent locations ( 7 ) form individual items of information, wherein the transparent locations ( 7 ) are produced with a laser beam ( 19 ) by perforating the metal layer ( 6; 11 ). Besides being used as a lamination foil the decorative foil can also be used as a packaging foil.

This application claims priority based on an International Applicationfiled under the Patent Cooperation Treaty, PCT/EP01/14970, filed on Dec.18, 2001, and German Patent Application No. 100 64 616.6, filed on Dec.20, 2000.

BACKGROUND OF TILE INVENTION

The invention relates to a decorative foil and a method of marking thedecorative foil.

Such decorative foils are used for safeguarding and protecting markingsand inscriptions, photographs and other indicia on documents such aspasses, identity cards, credit cards, banknotes etc, or for packagingvaluable articles.

U.S. Pat. No. 5,331,443 describes a method in which a freshly embossedand light-diffracting relief structure covered by a reflection layer canbe individualised by applying marking thereto. The reflection layer islocally removed by means of laser beams and then covered with anadhesive layer. The disadvantage of this method is that the individualmarking has to be applied prior to finishing of the layer compositestructure by application of the adhesive layer.

It is also known (U.S. Pat. No. 2,590,906) that a dielectric coated witha metal forms an interference filter which in daylight reflectsbrilliant interference colors. U.S. Pat. No. 3,858,977 describes thesuitability of multi-layer interference filters as an authenticityfeature for documents. In accordance with U.S. Pat. No. 3,338,730structured surfaces which do not diffract daylight are covered with suchinterference filters in order to obtain an attractive packaging materialwhich lights up in the interference colors.

WO 98/19869 describes a method of perforating documents by means offocussed laser light. The density of the holes produced in the documentand the diameter of the holes are determined by a pattern of anoriginal. For that purpose an optical sensor senses the original andconverts the recognised gray tones of the original into density anddiameter of the holes which are burnt in the document. In that way it ispossible to produce images, portraits or letter images which can be seenwhen looking through the document and which are practically impossibleto counterfeit. Uses of that method are described in the articleentitled ‘Application of laser technology to introduce security featureson security documents in order to reduce counterfeiting’ by W Hospel inProceedings of SPIE, Vol 3314, 28–30 Jan., 1998, pages 254–259.

The article ‘Search for effective document security by“inventioneering”’ by J D Brongers in Proceedings of SPIE, Vol 3314,January, 1998, pages 29–38 describes that intensive, finely focussedlaser light is used to remove color layers on the surface of a substratein a predetermined pattern from a print image without damaging thesubstrate itself.

EP 0 201 323 B1 describes the layer structure of plastic foils whichinclude embossed holograms with transparent reflection layers. Thematerials suitable for the layer structure and the reflection layer aresummarised in that document.

Transparent dielectrics with a very high refractive index for increasingthe reflection capability in respect of diffraction structures are knownfrom WO 99/47983.

SUMMARY OF THE INVENTION

The object of the invention is to provide an inexpensive decorative foilwhich is suitable for marking and for lamination on to a document orpackaging, and a method for introducing items of information into thedecorative foil.

In accordance with the invention the specified object is attained by thefeatures recited in the characterising portions of claims 1 and 15.Advantageous configurations of the invention are set forth in theappendant claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in greater detail hereinafterand illustrated in the drawing in which:

FIG. 1 is a view in cross-section of a decorative foil on a substrate,

FIG. 2 shows a view in cross-section of another embodiment of thedecorative foil,

FIG. 3 a shows a view in cross-section of a motif or subject in thedecorative foil,

FIG. 3 b shows the motif or subject as a plan view on to the decorativefoil,

FIG. 4 shows plan views of configurations of the decorative foil,

FIG. 5 shows a plan view of a decorative foil strip, and

FIG. 6 shows a document laminated with the decorative foil.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 reference numeral 1 denotes a layer composite structure for adecorative foil, reference 2 denotes a base foil, reference 3 denotes adielectric layer, reference 4 denotes a cover layer, reference 5 denotesa substrate, reference 6 denotes a metallic layer, reference 7 denotes atransparent location without a metallic layer 6 while reference 8denotes indicia and reference 9 a color area on the substrate 5. Thesubstrate 5 is at least part of a document such as a banknote, personalidentity pass, pass, identity card, credit card and so forth.

The layer composite structure 1 is built up on a transparent base foil2. In a simple embodiment of the layer composite structure 1 the inwardside of the base foil 2 is completely covered with a thin layer 3 of atransparent dielectric. Then, at least in partial regions, thedielectric layer 3 is followed by a reflective metallic layer 6. Themetallic layer 6 can be applied directly only in the partial regions orinitially over the full surface area involved, in which case then themetallic layer 6 is removed again outside the partial regions. The layercomposite structure 1 is finished as a decorative foil by covering overthe dielectric layer 3 and the metallic layer 6 respectively with thecover layer 4.

If the decorative layer is intended to be laminated on to a substrate 5the material of the cover layer 4 has adhesiveness. The layer compositestructure 1 is brought into contact with the cover layer 4 with thesubstrate 5 and joined to the substrate 5 by activation of the adhesiveof the cover layer 4. For example the cover layer 4 comprises a hot meltadhesive whose adhesiveness is only developed by heating the layercomposite structure 1 and the substrate 5 to a temperature of over 100°C. Such hot melt adhesives are available on a polyurethane orpolyethylene base. In another embodiment of the layer compositestructure 1 the material of the cover layer 4 is a cold adhesive whichis activated by pressing the layer composite structure 1 against thesubstrate 5. The use of a cold adhesive means that the free surface ofthe cover layer 4 is to be covered with a pull-off foil (not shown here)immediately after application of the cold adhesive. The pull-off foilhas to be removed before the layer composite structure 1 is stuck on tothe substrate 5. Materials which can be used for the cover layer 4 arementioned in EP 0 201 323 B1 in the section entitled ‘adhesive layer’ onpage 13.

In an embodiment hot-laminatable decorative foils, between a lacquerlayer 10 and the base foil 2, advantageously have a separation layer 10′which is indicated in FIG. 1 by a broken line and which is between about500 nm and 1 μm in thickness so that, after the decorative foil has beenlaminated on the substrate 5, the base foil 2 can be pulled off. Thepart of the layer composite structure 1 which remains on the substrate 5is less than 20 μm thick.

In another embodiment, the layer composite structure 1 additionallyincludes a transparent metal film 11 between the base foil 2 or thelacquer layer 10 and the dielectric layer 3. The metal film 11 coversover the first boundary layer 13 in such a way that the dielectric layer3 is embedded between the metal film 11 and the metallic layer 6.

The base foil 2, on the side towards the dielectric, can have atransparent lacquer layer 10 in order to achieve better adhesion for thedielectric and/or easier mechanical deformability of the surface of thebase foil 2, which is towards the dielectric, when the lacquer layer 10is better suited for shaping a microscopically fine relief of a surfacepattern, than the base foil 2. The surface pattern includes amosaic-like arrangement of diffraction elements and other surfaceelements with scattering or reflecting properties or it is a hologram.The lacquer layer 10 is applied at least approximately twice as thick asthe profile height of the microscopically fine relief of the surfacepattern; the thickness of the lacquer layer 10 is in the range ofbetween 150 nm and 2 μm. The operation of shaping the relief can beeffected prior to or after the step of applying the dielectric layer 3or also only into the metallic layer 6.

Transparent material is optically clear and transmits the entirespectrum of visible light (=material which is as clear as glass) or onlycertain spectral regions thereof (=colored material).

Foil webs of polyvinyl chloride (PVC), polycarbonate (PC), polyethyleneteraphthalate (PETP), polyethylene (PE), polypropylene (PP), cellophaneor a foil of another transparent plastic material, which arecommercially available in widths of between about 30 cm and 120 cm, aresuitable as the base foil 2. What is common to those foils are theirhigh level of transparency and their great tensile strength even insmall layer thicknesses. Typically the layer thicknesses of those foils,depending on the foil material, are in the range of between 200 μm andless than 9 μm. The refractive index n_(d) of those materials is in therange of values of between 1.50 and 1.60 or directly adjacent to thatrange by a few tenths. Good adhesion between the base foil 2 and theother layers of the layer composite structure 1 is essential.

The lacquer layer 10 is applied on the base foil 2 in the form of alow-viscosity lacquer. Examples of various transparent lacquers arereferred to in above-mentioned EP 0 201 323 B1, page 5, section entitled‘Transparent hologram forming layer’, as well as solvent-bearing andalso solvent-free lacquer, for example hardening by means of ultravioletlight. A composition for a lacquer with solvent for the thermoplasticlacquer layer 10 is set out at line 15 on page 19 of EP 0 201 323 B1.

In an embodiment the dielectric layer 3 involves a substantially uniformapplication of a thickness s, wherein the thickness s is at most 300 nm,but typical values are between 50 nm and 200 nm. Suitable dielectricswhich are transparent, in the visible part of the spectrum ofelectromagnetic waves are referred to in Table 1 of above-mentioned EP 0201 323 B1. The selected dielectric is applied in a vacuum by means ofvapor deposition or sputtering to the base foil 2 or the lacquer layer10 respectively. Preferred transparent dielectrics are MgF₂, ZnO, SiO,SiO₂, TiO₂ and ZnS as well as the chalcogenide substances which areknown from WO 99/47983 and which are distinguished by a very highrefractive index, such as Ge₃₀Sb₁₀S₆₀ (n=2.25), As₅₀Ge₂₀Se₃₀ (n=2.95),and Ge₂₀Sb₂₅Se₅₅ (n=3.11). White light which penetrates through the basefoil 2 into the layer composite structure 1 at an angle of incidence ais partially reflected at a first interface 13 between the base foil 2or the lacquer layer 10 and the metal film 11 or the dielectric layer 3and at a second interface 14 between the dielectric layer 3 and themetallic layer 6 or the cover layer 4, in which case the degree ofreflection is determined by the jump in the refractive index in thetransition at each interface 13, 14 and the angle of incidence α. Lightbeams 15 which have penetrated into the dielectric layer 3 and whichwere reflected at the second interface 14 cover a greater distance thanlight waves 16 which were already reflected at the first interface 13.The light beams 15 and the light beams 16 involve a phase difference, byvirtue of the difference in the distance covered, and in that respect asa consequence of interference effects a reflected light 17 is producedfrom the light beams 15 and the light waves 16, in respect of whichlight certain wavelength ranges are extinguished from the spectrum ofthe white light 12. Therefore in daylight the decorative foil shines inan interference color which is dependent on the thickness of thedielectric layer 3 and the reflection angle β, that is to say α=β. Theintensity of the interference color of the reflected light 17 isincreased if the metallic layer 6 and/or the metal film 11 is present.

In a further embodiment, instead of those transparent dielectrics, thedielectric layer 3 comprises one of the lacquers referred to for thelacquer layer 10. As the refractive indices of the materials for thebase foil 2 and the lacquer layer 10 respectively and for the coverlayer 4 differ only very slightly from the dielectric layer 3, theintensity of the interference colors is low. The dielectric layer 3 istherefore preferably disposed between the metal film 11 and the metalliclayer 6.

In another embodiment of the layer composite structure 1 instead of theadhesive, the same material is applied for the cover 4 as for thelacquer layer 10. Such a foil can be used as a packaging foil forexclusive articles and gifts. The decorative foils provided with a hotmelt adhesive can also be used for packaging. Therefore ‘decorativefoil’ denotes both a decorative lamination foil and also a decorativepackaging foil.

The microscopically fine relief of the optically diffractive surfacepattern, which relief is optionally formed in the lacquer layer 10,diffracts at the first and second interfaces 13 and 14 the incidentlight at the wavelength λ at the diffraction angles γ determined by thewavelength λ and the respective grating parameters such as gratingvector, relief profile, spatial frequency f, azimuth and so forth. Thelight diffracted at the first interface 13 involves a difference in thedistance covered, in comparison with the light diffracted at the secondinterface 14. Because of the interference effects the light diffractedat the diffraction angle γ in the m-th order, of the wavelength λ can beextinguished so that parts of the surface pattern, instead of appearingin brilliant colors, appear in a mixed color or indeed gray to black. Ifthe grating vector is in the plane of the light 12 incident at the angleα, the diffraction angle γ is determined by the relationship γ=± arc sin[m·f·λ+sin(α)]. To simplify the view in FIG. 1 changes in direction ofthe light beams 12, 15, 16, as a consequence of refraction effects, arenot shown.

The metallic layer 6 and the metal film 11 comprise a metal from thepreferred group: aluminum, silver, gold, chromium, copper and tellurium.Those metals are suitable for vapor deposition of the metallic layer 6or the metal film 11 and are chemically insensitive in the layercomposite structure 1. The metallic layer 6 is intended to reflect alarge part of the incident light beams 12. Therefore the thickness D ofthe metallic layer 6 is more than 50 nm, preferably between 50 nm and300 nm. In contrast thereto the metal film 11 must be transparent for alarge part of the incident light 12; therefore the metal film is of alayer thickness d of a value of 50 nm or less; a typical range for thelayer thickness d is between 5 nm and 15 nm. The layer thicknesses D andd are dependent on the metal and the wavelength λ of the incident light12 and 15 respectively, as is set forth in ‘Optical properties of thinsolid films’ by O S Heavens, Butterworths Scientific Publications,London (1955), pages 156–170. In a particular configuration thethickness D (FIG. 1) of the metallic layer 6 is also so slight that themetallic layer 6 is as transparent as the metal film 11. Thereflectivity in the layer composite structure 1 is higher than in thecase of the layer composite structure 1 without metal layers 6, 11 butlower than in the case of the decorative foil with a completelyreflective metal layer 6. The layer composite structure 1 is thereforecolored transparent over its entire surface area and reflects coloredlight 17.

A writing device 18 includes a pulsed light source, for example a laser,light emitting diode and so forth, with a focusing device of short focallength. A high-power energy beam 19 which is briefly emitted by thelight source is focussed by means of the focusing device through thebase foil 2 into the layer composite structure 1 in such a way that thefocus of the energy beam 19 and thus the highest power density is in theregion of the metallic layer 6. The power density decreases rapidlyoutside the focus on an axis of the energy beam 19. The thin metalliclayer 6 and a metal film 11 if present are locally rapidly heated abovethe melting point of the metal. When they cool down the metal at theinterfaces 13, 14 hardens to form very fine globules which are notvisible to the eye. The energy beam 19 perforates only the metal layers6, 11 but not the other layers of the layer composite structure 1 sothat the layer composite structure 1 has the transparent location 7 atthe perforation. In the focus the diameter of the energy beam 19 istypically some 10 μm. The pulse duration and the delivered power of theenergy beam 19 determine the diameter of the transparent location 7produced with a pulse. A plurality of pulses of the energy beam 19,applied to immediately juxtaposed locations, produce the roundtransparent location 7 of a size of up to 1 mm or a transparent location7 in the form of a line which is up to 1 mm in width. The pulseduration, the power and the wavelength of the energy beam 19 are to beso selected that the energy beam 19 on the one hand deposits as littleenergy as possible in the dielectric layer 3, in the plastic layers 2, 4and 10 and in the indicia 8 or the color area 9, so that the heatingeffect thereof is kept within limits and no damage to the layercomposite structure 1 or the substrate 5 occurs, and on the other handit is strongly absorbed by the metal of the layers 6, 11. The foil webswith the layer structure 1 can be written or engraved with that devicein the surface portions with the metallic layer 6. For that purpose, ona rolling transfer apparatus, the foil webs are unrolled from onewinding and then rolled on to the other winding again. During therolling transfer operation from one winding to the other, the foil webis pulled through beneath the computer-controlled energy beam 19 whichis displaceable transversely over the foil web, and the transparentlocations 7 are produced in a predetermined pattern in the layercomposite structure 1.

In the embodiment of the decorative foil shown in FIG. 2 the layercomposite structure 1 has the dielectric layer 3, the thickness s ofwhich is modulated in the direction z at an angle θ (FIG. 4) withrespect to the travel direction x (FIG. 4) of the decorative foil with afunction F(z). The angle θ is of a value in the range of between 30° and90°. The function F(z) is for example periodic, as shown in FIG. 2, inwhich respect a period p measured in the direction z is of the order ofmagnitude of between some centimeters and decimeters; preferably thelength of the period p is selected from the range 1 cm≦p≦50 cm. Thatmodulation is produced by irregular vapor deposition of the material forthe dielectric layer 3. The function F(z) changes the values of thethickness s between a minimum value M and the maximum value A. Forexample the minimum value M is in the range ≦50 nm while the range forthe maximum value extends between 100 nm and 300 nm. The thickness stherefore varies very slowly over the surface area of the decorativefoil. For the sawtooth function F(z) shown in the view in FIG. 2 thegradient of the thickness s is in the range of between 2 nm/cm and 250nm/cm if the above-mentioned values are assumed to apply in respect ofthe minimum value M, the maximum value A and the period p. For otherfunctions F(z) the thickness s varies between the minimum value M andthe maximum value A at a maximum gradient in respect of the thickness s,which ranges in the same range as in the case of the periodic sawtoothmodulation.

Since, as stated above, the color of the light 17 reflected by thedecorative foil (FIG. 1) depends on the thickness s of the dielectriclayer 3, the color of the reflected light 17 changes over the area ofthe layer composite structure 1 in accordance with the modulation of thethickness s, which is afforded by the function f(z). Such a layercomposite structure 1 has a striking appearance, with and withoutoptical-diffraction surface patterns in the base foil 2 and the lacquerlayer 10 respectively. A particularly striking pattern is obtained if,after the application of a first dielectric layer 3 which is modulatedin the direction (z), in a second installation a second dielectricconsisting of the same or another material is deposited on that firstlayer, the thickness of application of the second dielectric beingmodulated for example transversely with respect to the direction z. Inthis example a net-shaped colored pattern appears in the reflected light17 on the surface of the decorative foil.

In an embodiment of the dielectric layer 3 shown in FIG. 3 a themodulation is binary, that is to say the dielectric layer 3 has only twovalues in respect of the thickness s (FIG. 2). The thinner layer in thebackground surfaces 40 is of a value in respect of the thickness s_(min)of less than 200 nm and the thicker layer in motif or subject surfaces41 is of a value in respect of thickness s_(max) in the range of between100 nm and 300 nm, wherein the thickness s_(max) is at least 25 nmthicker than the thickness s_(min). In a special case the thicknesssmin=0; that is to say the dielectric layer 3 comprises the motifsurfaces 41 which are not joined together and which are separated by thebackground surfaces 40 with or without a metallic layer 6. In an examplea subject or motif comprising motif surfaces 41 and consisting of thesame or another dielectric is so applied to the uniformly applieddielectric layer 3 that the dielectric layer 3 is of the thicknesss_(max) in the motif surfaces 41 of the motif and the thickness s_(min)outside the motif surfaces 41. The thickness s of the dielectric layer 3changes in accordance with the motif and is therefore modulatedtherewith. When the layer composite structure 1 is observed the motif isvisible through the base foil 2. The motif surfaces 41 differ from thebackground surfaces 40 by virtue of a different interference color ofthe reflected light 17 (FIG. 1). Production of the motif surfaces 41 isadvantageously effected by applying an additional layer of thedielectric, for example through a mask (not shown here), or by means ofa per se known printing process, in which case preferably theabove-mentioned transparent lacquer is applied in the motif surfaces 41,as far as the required thickness s_(max).

If the motif surfaces 41 which are applied in succession in variouslayers with the same dielectric or with different dielectrics overlap,the arrangement of the motif surfaces 41 affords step modulation of thelayer 3 comprising the dielectric or the dielectrics.

FIG. 3 b is a plan view showing the structure of the dielectric layer 3,with the raised motif surfaces 41 being shown in rastered form in thedrawing. The dimensions of the motif surfaces 41 which are shown in thedrawing by means of a line raster are mostly greater than 0.3 mm, otherthan in the case of rastered images 42 whose motif surfaces 41 have adot raster with a resolution of up to 400 dpi (=16 pixels/mm). If grayvalues of the images 42 are illustrated by the density of the dotraster, it is possible to use black-and-white portraits as an originalfor the images 42. The motif surfaces 41 and/or the images 42 form apattern 43. Mention is to be made in this context of the ink jetprinting process with which the motif surfaces 41 of the rastered images42, texts and lines are transferred on to the dielectric layer 3 inaccordance with an original stored in a computer in electronic form.

Reference is now again made to FIG. 1. As the layer 6 is practically nolonger transparent by virtue of its layer thickness D the layercomposite structure 1, in the surface portions with the metallic layers6, covers the indicia or color areas 9 which are under the layercomposite structure 1. In contrast thereto the layer composite structure1 is transparent in the other surface portions where the transparentdielectric layer 3 directly adjoins the cover layer 4. The indicia 8 orcolor areas 9, or the surface 29 of the substrate 5, which are under thetransparent decorative foil, are clearly visible insofar as visibilityis not disturbed by the colored reflected light 17.

FIG. 4 shows a portion from a foil web with the layer compositestructure 1 which extends in the direction x. After application of thecover layer 4 (FIG. 2) and the optional pull-off foil the widedecorative foil is divided along the lines 20, 21, 22 into strips 23 ofpredetermined width and marketed.

The view in FIG. 4 shows on the left-hand side an embodiment of thedecorative foil in which the dielectric layer 3 (FIG. 1) is of athickness s (FIG. 1) which is as uniform as possible. In an embodimentof the strip 23 the dielectric layer 3 has the metallic layer 6 (FIG. 2)in a strip portion 24 at least at the second interface 14 (FIG. 1) whilestrip-shaped areas 26, 26′ of the layer composite structure 1 aretransparent. In the view in FIG. 4, in the strip 23, the strip portion24, 24′ which is emphasised by a coarse dot raster and the area 26, 26′are separated by a broken line. In an embodiment the strip portion 24has window surfaces 25 at regular spacings in the metallic layer 6, thecomposite layer structure 1 being transparent in the window surfaces 25.In an advantageous embodiment, the microscopically fine relief of theabove-mentioned surface pattern 27 is embossed in the region of thewindow surfaces 25 in order to enhance the level of counterfeitingsecurity. The surface pattern 27 can also extend over into zones of thestrip portion 24, which zones adjoin the window surfaces 25.

In another embodiment of the decorative foil which is shown on theright-hand side in FIG. 4, the dielectric layer 3 involves the periodicmodulation in respect of thickness s in the indicated direction z. Thestrip pattern which appears colored differently in the reflected lightis emphasised using graphic means in the view in FIG. 4 by means ofstrip-shaped surfaces which alternately have a dense raster and a coarseraster or no raster respectively. In the areas 26′ between the line 21or 22 and the most closely adjacent broken line dielectric layer 3 doesnot have any metal covering and the area 26′ is transparent. The coarseraster in the strip 24′ between the line 22 and the broken line to theleft thereof symbolically represents the presence of the metallic layer6 so that the composite layer structure 1 is opaque in the strip 24′.

In a further embodiment of the composite layer structure 1 thedielectric layer 3 is covered over its entire area at least with themetallic layer 6 so that the entire decorative foil is intensivelycolored but not transparent. Depending on the respective purpose of useinvolved the decorative foil is marketed in a condition of not beingseparated in respect of width or being divided into strips 23 of themost widely varying widths.

FIG. 5 shows a portion of the strip 23 viewing on to the base foil 2(FIG. 3 a). In the reflected light 17 (FIG. 1) the pattern 43 stands outfrom the interference color of the background surfaces 40 in and aroundthe pattern 43 because of the modulation of the thickness s (FIG. 2) ofthe dielectric layer 3 (FIG. 3 a), in a different interference color.The motif 43 shown in FIG. 3 b is repeated for example at a regularspacing.

FIG. 6 shows a use of the strip 23 illustrated in broken line, with thewindow surfaces 25, for sealing an identity card 28. The identity card28 comprises the substrate 5 (FIG. 1) which, on its surface 29 (FIG. 1)to be protected with the lamination foil, has the color area 9 and theindicia 8 (FIG. 1) and an area for a photograph 30 of the holder of theidentity card. The indicia 8 are general details about the card issuerin a text area 31. Upon delivery of the card the photograph 30 is stuckinto the area provided for that purpose or is directly introduced on tothe substrate and for example the name of the holder and his identitynumber, in this case ‘123-B-10’ written into a labelling strip 32. Inorder to prevent subsequent alteration to the identity card 28 a portionof the lamination foil from the strip 23 is stuck on to the card in sucha way that the photograph 30 is visible through the window surface 25and the labelling strip 32 is visible through the area 26. The text area31 and the color area 9 are covered by the opaque surface portions ofthe strip portion 24 of the lamination foil. After the glueing operationthe identity card 28 is cut in such a way that there are no projectingremains left from the lamination foil.

Pieces of the lamination foil are also used for securing the individualdetails of a pass, a visa in a pass, banknotes, packaging etc.Hereinafter those uses are described by reference to the example of an‘identity card’.

The writing device 18 (FIG. 1) is displaced over the surface of thelayer composite structure 1 to be written to, by means of a co-ordinatecontrol system, in order to produce the transparent locations 7 (FIG. 1)in a predetermined raster pattern, in such a way that the indicia 8under the lamination foil, for example in the text area 31 and, if nospecial window surface 25 is provided in the lamination foil, thephotograph 30, are visible through the transparent locations of thelayer composite structure 1.

Further individual items of information are advantageously also writtenby means of the energy beam 19 (FIG. 1) of the writing device 18 in theregion of the reflecting strip portion 24 on the identity card 28 byvirtue of the destruction of the metallic layer 6 (FIG. 1), such as forexample alphanumeric characters 33, emblems 34, a bar code 35 orrastered images. Through the transparent locations 7 (FIG. 1), it ispossible to see the color of the subjacent surface 29. The transparentlocations 7 form a dot and/or line pattern which strikingly stands outin the invariable color of the surface 29 from the reflecting surfaceportions 36 (FIG. 1) of the layer composite structure 1. Instead of thedot and/or line pattern the transparent locations 7 also have shapes ofthe alphanumeric characters 33, the emblems 34 and the bar code 35 andare visible in the color of the surface 29. In the illustrated examplethe text 33 is the identification number ‘123-B-10’ produced from thelabelling strip portion 32 over the color area 9. In another embodimentthe rectangular transparent locations 7 and the reflective surfaceportions 36 separating the transparent locations 7, of different width,form the bar code 35, in which case the rectangular transparentlocations 7 represent bars and the reflective surface portions 36represent separating spacings in the bar code 35. In the case of thebanknote the serial number is the individual element which, after thelamination foil is stuck on, is to be written in, in visually coded formand/or machine-readably.

In another embodiment the writing device 18 is equipped with theapparatus known from above-mentioned WO 98/19869 and is capable ofreading off an image original, breaking it down into small pictureelements (=pixels) arranged in the raster, and producing transparentlocations 7 in the form of a circular area in the layer compositestructure 1 in the metallic layer 6 in the same raster in such a waythat an image of the image original is produced in the layer compositestructure 1. Gray values of the pixels are reproduced by differingdiameters of the transparent circular areas. Degrees of resolution of upto 400 dpi (=16 pixels per mm) or more can be achieved.

By way of example the lamination foil additionally includes theoptical-diffraction surface pattern 27 in the form of a guillochepattern in the region of the window surface 25. As the window surface 25with the guilloche pattern is never precisely placed on the area for thephotograph, it is possible to recognise any exchange of the photograph30 (in the context of an attempt at counterfeiting) by virtue of a breakin the line configuration of the guilloche pattern. In addition in anembodiment the lamination foil has the pattern 43 produced by means ofmodulation of the thickness s (FIG. 2) of the dielectric layer 3 and/orthe periodic modulation with a strip or net pattern.

Whether the decorative foils are later used as lamination foils orpackaging foils, they can be written to, with the above-discussedpatterns, on the above-mentioned rolling transfer installation. One useis for labelling a packaging foil with the logo or the trade mark of theproduct to be packaged.

Without departing from the idea of the invention, instead of thedielectric layer 3 (FIG. 1) comprising a single dielectric a dielectriclayer 3 comprising a plurality of layers, as is known for example fromU.S. Pat. No. 3,858,977, is also to be read into the foregoingdescription.

1. A decorative foil with a layer composite structure comprising atransparent base foil, a transparent cover layer and a transparentdielectric layer arranged between the base foil and the cover layer,wherein a metallic layer is arranged between the dielectric layer andthe cover layer in surface portions, wherein a transparent metal film isarranged between the dielectric layer and the base foil in regionscorresponding to the surface portions of the metallic layer, and whereina first interface in which the refractive index abruptly changes isprovided between the dielectric layer and the base foil.
 2. A decorativefoil as set forth in claim 1, wherein the cover layer is adapted forgluing the layer composite structure onto a substrate.
 3. A decorativefoil as set forth in, claim 1 wherein the metal film comprises a metalselected from the group consisting of aluminum, silver, gold, chromium,copper and tellurium.
 4. A decorative foil as set forth in claim 3,wherein the metal in the metal film has a transparency of at least 50%.5. A decorative foil as set forth in claim 1, wherein the metallic layercomprises a metal selected from the group consisting of aluminum,silver, gold, chromium and tellurium.
 6. A decorative foil as set forthin claim 5, wherein the metallic layer has a layer thickness in therange of from 50 nm to 300 nm.
 7. A decorative foil as set forth inclaim 1, wherein the layer composite structure further comprises atransparent thermoplastic lacquer layer between the first interface andthe base foil.
 8. A decorative foil as set forth in claim 1, wherein thedielectric layer comprises a transparent dielectric selected from thegroup consisting of MgF₂, ZnO, TiO₂, SiO, SiO₂, ZnS and a chalcogenidesubstance.
 9. A decorative foil as set forth in claim 8, wherein thethickness of the dielectric layer is less than 300 nm.
 10. A decorativefoil as set forth in claim 1, wherein the thickness of the dielectriclayer is a function of the location of changes over the surface of thelayer composite structure and wherein the thickness of the dielectriclayer has a gradient of between 2 nm/cm and 250 nm/cm.
 11. A decorativefoil as set forth in claim 9, wherein the thickness of the dielectriclayer is modulated periodically at least in a direction over the surfaceof the layer composite structure.
 12. A decorative foil as set forth inclaim 1, wherein the dielectric layer in partial regions has a lightdiffracting, microscopically fine relief structure of a surface patternat the first interface towards the base foil and/or at a secondinterface towards the cover layer.
 13. A decorative foil as set forth inclaim 1, wherein at least the metallic layer is perforated in a raster,in a dot and/or line pattern or in the form of alphanumeric charactersand emblems, in such a way that the layer composite structure istransparent at said locations.